1. Field of the Invention
The present invention relates to a method for making emergency calls in cordless telecommunications systems by means of a special emergency call transmission procedure wherein an emergency call connection is made regardless of whether the system contains mobile parts which do or do not have access authorization to base stations.
2. Description of the Prior Art
In telecommunications systems with a telecommunication transmission link between a telecommunication source and a telecommunication sink, transmission and reception units are used for processing and transmitting telecommunications, in such units:
1) it is possible for the processing and transmission of telecommunications to take place in a preferred transmission direction (simplex mode) or in both transmission directions (duplex mode);
2) the processing of telecommunications is analog or digital;
3) the transmission of telecommunications via the long-distance transmission link takes place wirelessly on the basis of various telecommunications transmission methods such as FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and/or CDMA (Code Division Multiple Access); for example, according to radio standards such as DECT, GSM, WACS or PACS, IS-54, PHS, PDC etc. [cf. IEEE Communications magazine, January 1995, pages 50 to 57; D. D. Falconer et al: xe2x80x9cTime Division Multiple Access Methods for Wireless Personal Conmunicationsxe2x80x9d] and/or in a wirebound fashion.
xe2x80x9cTelecommunicationxe2x80x9d is a superordinate term which stands both for the signal contents (information) and for the physical representation (signal). Despite a telecommunication having the same contentxe2x80x94that is to say the same informationxe2x80x94different signal forms may occur. Thus, for example, a telecommunication relating to an object can be transmitted
(1) in the form of an image, or
(2) as a spoken word,
(3) an a written word,
(4) as an encrypted word or image.
The method of transmission according to (1) . . . (3) is normally characterized by continuous (analog) signals, whereas in the transmission method according to (4) discontinuous signals (e.g., pulses, digital signals) are usually produced.
Cordless telecommunications systems of the type defined above are, for example, DECT systems [Digital Enhanced (earlier: European) Cordless Telecommunication; cf. (1): Nachrichtentechnik Elektronik. [Telecommunications electronics] 42 (1992) January/February No. 1, Berlin, DE; U. Pilger xe2x80x9cStruktur des DECT-Standardsxe2x80x9d [Structure of the DECT Standard], pages 23 to 29 in conjunction with the ETSI publication ETS 300175-1 . . . 9, October 1992; (2): Telecom Report 16 (1993), No. 1, J. H. Koch: xe2x80x9cDigitaler Komfort fxc3xcr schnurlose Telekommunikationxe2x80x94DECT-Standard erxc3x6ffnet neue Nutzungagobietesxe2x80x9d [Digital convenience for cordless telecommunicationsxe2x80x94DECT standard opens up new fields of use], pages 26 and 27; (3): tec February, 1993xe2x80x94Das technische Magazin von Ascom xe2x80x9cWege zur universellen mobilen Telekommunikationxe2x80x9d [The technical magazine from Ascom xe2x80x9cWays toward universal mobile telecommunications], page 35 to 42; (4): Philips Telecommunication Review, Vol. 49, No. 3, September 1991, R. J. Mulder: xe2x80x9cDECT, a universal cordless access systemsxe2x80x9d; (5): WO 93/21719 (FIGS. 1 to 3 with associated description)] or GAP systems (Generic Access Profile; ETSI publication prETS 300444, April 1995, Final Draft, ETSI, FR), which may be designed, for example, in accordance with the illustration in FIG. 1.
The GAP Standard is a subset of the DECT Standard and has the function of ensuring the interoperability of the DECT air interface, in particular, for public telecommunications applications.
Where DECT/GAP systems are referred to below, private and/or public systems are thus meant.
According to the DECT/GAP standard, it is possible, in accordance with the illustration in FIG. 1, to set up at a DECT/GLP base station BS a maximum of 12 connections according to the TDMA/FDMA/TDD method (Time Division Multiple Access/Frequency Division Multiple Access/Time Division Duplex) in parallel to DECT/GAP mobile parts MT1 . . . MT12 over a DECT/GAP air interface configured for the frequency range between 1.88 and 1.90 GHz. The number 12 results from the number xe2x80x9ckxe2x80x9d of time slots or telecommunications channels (k=12) available for the duplex mode of a DECT/GAP system. The connections here may be internal and/or external. When there is an internal connection, two mobile parts registered at the base station BS, for example the mobile part MT2 and the mobile part MT3, can communicate with one another. To set up an external connection, the base station BS is connected to a telecommunications network TKN, for example in line-bound form via a telecommunications connection unit TAE and/or a private branch exchange system NStA with a line-bound telecommunications network or, in accordance with WO 95/05040, in wireless form as a repeater station with a superordinate telecommunications network. When there in an external connection, it is possible to use a mobile part, for example the mobile part MT1, to communicate with a subscriber in the telecommunications network TKN via the base station BS, the telecommunications connection unit TAE or the private branch exchange system NStA. If the base station BS has, as in the case of the Gigaset 951 (Siemens cordless telephone, cf. Telcom report 16, (1993) Issue 1, pages 26 and 27), only one connection to the telecommunications connection unit TAE and/or to the private branch exchange system NStA, only one external connection can be set up. If the base station BS has, as in the case of the Gigaset 952 (Siemens cordless telephone; cf. Telcom report 16, (1993), issue 1, pages 26 and 27), two connections to the telecommunications network TKN, a further external connection, in addition to the external connection to the mobile part MT1, is possible from a line-bound telecommunications terminal TKE which is connected to the base station BS. In this context, it is in principle also conceivable for a second mobile part, for example the mobile part MT12, to use the second port for an external connection, instead of the telecommunications terminal TEE. While the mobile parts MT1 . . . MT12 are operated with a battery or an accumulator, the base station BS which is designed as a cordless small-scale exchange is connected to a voltage network SPN via a mains connection unit NAG.
FIG. 2 shows, on the basis of the publication Components 31 (1993), Issue 6, pages 215 to 218; S. Althammer, D. Brxc3xcckmann: xe2x80x9cHochoptimierte IC""s fxc3xcr DECT-Schnurlostelefonexe2x80x9d [Highly optimized ICs for DECT cordless telephones] the basic circuitry design of the base station BS and of the mobile part MT. According to the latter, the base station BS and the mobile part MT have a radio component FKT (with an antenna ANT which is assigned to transmitting and receiving radio signals) a signal processing device SVE and a central controller ZST which are connected to one another in the illustrated way. The radio component PXT contains such known devices such as a transmitter SE, a receiver EM and a synthesizer SYN. The signal processing device SVE contains, inter alia, a coding/decoding device CODEC. The central controller ZST has a microprocessor xcexcP, both for the base station BS and for the mobile part MT, with a program module PGM set up according to the OSI/ISO layer model [cf. (1): Instruction sheetsxe2x80x94Deutsche Telekom, year 48, February 1995, pages 102 to 111; (2): ETSI publication ETS 300175-1 . . . 9, October 1992], a signal control component SST and a digital signal processor DSP, which are connected to one another in the way illustrated. Of the layers defined in the layer model, only the directly essential first four layers are illustrated for the base station BS and the mobile part MT. The signal control component SST is designed as a Time Switch Controller TSC in the base station BS and as a Burst Mode Controller BMC in the mobile part MT. The essential difference between the two signal control components TSC, BMC consists in the fact that the base station-specific signal control component TSC additionally assumes switching functions in comparison with the mobile part-specific signal control component BMC.
The principal method of operation of the circuit units specified above is described, for example, in the publication Components 31 (1993), Issue 6, pages 215 to 218, cited above.
The described circuitry design according to FIG. 2 is supplemented in the base station BS and the mobile part MT in accordance with their function in the DECT/GAP system according to FIG. 1 by means of additional function units.
The base station BS is connected to the telecommunications network TKN via the signal processing device SVE and the telecommunications connection unit TAE or the private branch exchange system NStA. As an option, the base station BS also can have a user interface (functional units shown with broken lines in FIG. 2), which includes, for example, an input device EE designed as a keypad, a display device AE designed as a display, a hand-held unit SHE designed as a handset with microphone MIF and earphone HK, as well as a ringer TRK.
The mobile part MT has a user interface which is possible with the base station BS as an option and which has the control elements described above, that are associated with this user interface.
FIG. 3 shows, taking the DECT system according to FIG. 1 as a starting point, a cellular DECT/GAP multisystem CMI (Cordless Multicell Integration) in which a plurality of the DECT/GAP systems TKS described above, each with one base station BS and one or more mobile parts MT present at a given geographical location for example a concentrated (in a xe2x80x9chot spotxe2x80x9d arrangement) in an administration building with large open-plan offices. However, instead of an xe2x80x9cenclosedxe2x80x9d geographical location, such as the administration building, an xe2x80x9copenxe2x80x9d geographical location with strategic telecommunication significance, for example squares in large cities with a high traffic volume, a large collection of commercial units and large volumes of people moving, is also possible for the installation of a cellular DECT/GAP multisystem CMI. A number of the base stations BS arranged in the open-plan office are designed here as antenna diversity base stations, in contrast to the base stations according to WO 95/10764 shown in FIGS. 1 and 2, as. The concentration of the DECT/GAP systems TKS is so marked here (uninterrupted radio coverage of the geographical location), that individual DECT/GAP systems TKS operate in the same area as a result of the overlapping cellular DECT/GAP radio cells FB.
Depending on the degree of overlapping, the same area may mean that
a) a first base station BS1 of a first telecommunications system TKS1 is arranged in a first radio cell FB1 and a second base station BS2 of a second telecommunications system TKS2 is arranged in a second radio cell FB2 and can set up telecommunications connections to at least one mobile part MT1,2 
b) a third base station BS3 of a third telecommunications system TKS3 and a fourth base station BS4 of a fourth telecommunications system TKS4 are arranged in a common third radio cell FB3 and can set up telecommunications connections to at least one mobile part MT3,4.
FIG. 4 shows, using FIGS. 1 to 3 as a basis and with reference to the publication xe2x80x9cNachrichtentechnik Elektronik [Telecommunications Electronics] 42 (1992) January/February, No. 1, Berlin, DE; U. Pilger: xe2x80x9cStruktur des DECT-Standardsxe2x80x9d [Structure of the DECT Standard], pages 23 to 29 in conjunction with ETS 300175-1 . . . 9, October 1992xe2x80x9d the TDMA structure of the DECT/GKP system TKS. The DECT/GAP system is a hybrid system in terms of the multiple access methods in which, the FDMA principle, it is possible to transmit radio telecommunications on ten frequencies in the frequency band between 1.88 and 1.90 GHz from the base station BS to the mobile part MT from the mobile part MT to the base station BS (Time Division Duplex Mode) according to the TDMA principle in accordance with FIG. 4 in a prescribed time sequence. The time sequence is determined here by a multiple time frame MZR, which occurs every 160 ms and which has 16 time frames ZR, each with a time period of 10 ms. Information which relates to a C-, M-, N, P-, Q-channel defined in the DECT Standard is transmitted separately to the base station BS and mobile part MT in these time frames ZR. If information for a plurality of these channels is transmitted in one time frame ZR, the transmission takes place according to a priority list where M greater than C greater than N and P greater than N. Each of the 16 time frames ZR of the multiple time frame MZR is divided, in turn, into 24 time slots ZS (each with a time period of 417 xcexcs) of which 12 time slots ZS (time slots 0 . . . 11) are intended for the transmission direction xe2x80x9cbase station BSxe2x86x92mobile part MTxe2x80x9d and a further 12 time slots ZS (time slots 12 . . . 23) are intended for the transmission direction xe2x80x9cmobile part MTxe2x86x92base station BSxe2x80x9d. In each of these time slots ZS, information with a bit length of 480 bits is transmitted in accordance with the DECT Standard. Of these 480 bits, 32 bits are transmitted as synchronization information in a SYNC field and 388 bits are transmitted as useful information in a D field. The remaining 60 bits are transmitted as additional information in a Z field and as protective information in a xe2x80x9cguard timexe2x80x9d field. The 388 bits of the D field which are transmitted as useful information are in turn divided into a 64 bit-long A field, a 320 bit-long B field and a 4 bit-long xe2x80x9cX-CRCxe2x80x9d word. The 64 bit-long A field is composed of an 8 bit-long data header, a 40 bit-long data record with data for the C-, Q-, M-, N-, P-channels and a 16 bit-long xe2x80x9cA-CRCxe2x80x9d word.
Moreover, in addition to the abovementioned DECT/GAP systems, further future cordless telecommunications systems, which are based on the known multiple access methods FTMA, TDMA, CDMA (Frequency Division Multiple Access, Time Division Multiple Access, Code Division Multiple access), and hybrid multiple access methods formed therefrom, are possible for transmitting emergency calls.
For setting up telecommunications connections between the base station or stations BS and the mobile parts MT in the DECT/GAP systems in accordance with FIGS. 1 to 4, the procedure described below is provided, by way of example, in the DECT/GAP standard.
The base station BS (Radio Fixed Part RFP) in accordance with FIGS. 1 to 4 transmits the so-called dummy bearer on simplex transmission paths over the DECT air interface at regular time intervals, wherein the dummy bearer is broadcasting information which is received by the mobile part MT (Radio Portable Part RPP) in accordance with FIGS. 1 to 4 and being used by the latter for the synchronization and the connection set-up with the base station. The broadcast information does not necessarily have to be transmitted on a dummy transmission path (dummy bearer).
It is also possible for there to be no dummy transmission path because the base station already maintains at least one telecommunications connection, a so-called traffic transmission path (traffic bearer), to another mobile part, on which transmission path it then transmits the necessary broadcast information. In this case, the mobile part which wishes to have a telecommunications connection to the base station can receive the broadcast information, as in the case of the transmission of the broadcast information on the dummy transmission path.
The broadcast information containsxe2x80x94in accordance with the ETSI publication ETS 300175-3, October 1992, Chapter 9.1.1.1xe2x80x94information on access rights, system information and paging information.
Furthermore, the system information contains additional information which informs the mobile part whether the base station is a base station via which emergency calls can be transmitted (a subject which was publicly discussed in the ETSI-RES03R Gremium and ETSI-RES03N Gremium in the 1st half of 1996).
If the mobile part has received this additional information and if the respective mobile part also has access rights to the base station transmitting the additional information (for example if the mobile part is signed on and registered with the base station in accordance with WO 94/10785xe2x80x94Patent Claims iVm of the description of FIG. 4), a preconfigured emergency call number is automatically dialed and an emergency call connection is established. Such connection connects to emergency call service points in accordance with a special user interface procedure (for example, dialing of the emergency call number, 112, pressing of an emergency call key, selection of an item of menu information xe2x80x9cEMERGENCY CALLxe2x80x9d etc.) on the mobile part in accordance with the GAP Standard (cf. ETSI publication prETS 300444, April 1995) based on a set-up procedure for normal (usual) outgoing telecommunications connections via a direct call connection [cf. ETSI publication prETS 300444, April 1995, Chap. 8.10 (xe2x80x9cCC_INFO  less than  less than MULTI KEYPAD greater than  greater than )].
The procedure described above, for transmitting emergency calls in a DECT/GAP system, may be sufficient for private systems in which it can be assumed that the mobile parts have an access authorization to base stations. The defined procedure is inadequate, however, for public systems in which the access authorization is perhaps only given in individual cases.
Furthermore, in the procedure described above for transmitting emergency calls in a DECT/GAP system it is not always ensured that the mobile parts with an access authorization can transmit emergency calls to a base station in all cases. Thus, the case may occur in which the respective base station has no free channels any more, for example because of limited channel resources, or must decline a request or a wish for the transmission of an emergency call for other (unusual) reasons (cf. ETSI publication prETS 300444, April 1995, Chap. 8.2.2.3 and Chap. 8.8). The respective mobile part can then search for other base stations via which emergency calls still can be transmitted, but there is no guarantee that this search will be successful.
Furthermore, there remains the problem of how, if in the first place an emergency call has been successfully transmitted from a mobile part via a base station to an emergency service, that is to say an emergency call connection exists, when and who can terminate or clear this existing call connection again.
The transmission of emergency calls in wireless telecommunications systems is known in mobile radio systems in accordance with the GSM Standard (cf. publication by M. Mouly, M-B. Pautet: xe2x80x9cThe GSM System for Mobile Communicationsxe2x80x9d 1992, Int. Standard Book No. 2-9507190-0-7, pages 49, 453, 437 and 532-535).
The problems discussed above in conjunction with the transmission of emergency calls are not found in these mobile known radio systems.
The object on which the present invention is based consists in being able to make emergency calls in cordless telecommunications systems, in particular DECT/GAP systems, efficiently and reliably.
The idea on which the present invention is based lies in making emergency calls in cordless telecommunications systems by means of a special emergency call transmission procedure which allows for the fact that the system contains mobile parts which do or do not have access authorization to base stations and with which procedure an emergency call connection is produced in all cases.
Accordingly, in an embodiment of the present invention, a method is provided for making emergency calls in cordless telecommunications systems, wherein the method includes the steps of: initiating emergency calls to emergency call services points at cordless mobile parts using manual interface procedures via cordless base stations connected to the cordless mobile parts by telecommunication; transmitting, with the cordless mobile part, a first telecommunication with an emergency call-specific temporary first identification to the cordless base station; searching, with the mobile part using the telecommunication, at the cordless base station for an emergency call connection to the emergency call service point; distinguishing, with the cordless base station, between a usual communications request and an emergency call using the first identification received; responding, with the cordless base station, to the first telecommunication with a second telecommunication, and ensuring that a free telecommunications channel is set up for the emergency call connection; transmitting, with the cordless mobile part, to the cordless base station a third telecommunication with a first information element containing a call indicator for the emergency call and with a second information element containing a mobile part-specific second identification, and with a third infonnation element containing a zero contents indicator, wherein the third telecommunication causes the cordless base station to set up the emergency call connection to the emergency call service point; and setting up, with the cordless base station, the emergency call connection to the emergency call service point and informing the cordless mobile part of the setting up of the emergency call connection in response to the third telecommunication via a fourth telecommunication.
In an embodiment, the emergency call connection to the emergency call service point is set up by automatically dialing an emergency call number if the first cordless base station is a private cordless base station.
In an embodiment, the emergency call connection to the emergency call service point is set up automatically if the first cordless base station is a public cordless base station.
In an embodiment, the free telecommunications channel is set up for the emergency call connection by reserving one telecommunications channel from a plurality of telecommunications channels available in the cordless base station.
In an embodiment, the free telecommunications channel is set up for the emergency call connection such that if all of the plurality of telecommunications channels available in the cordless base station are occupied, one of the plurality of telecommunications channels is freed.
In an embodiment, the telecommunications channel includes both a radio channel between the cordless base station and the cordless information part and a voice/data channel between the cordless base station and the emergency call service point.
In an embodiment, the established emergency call connection within the cordless telecommunications system is cleared down by the cordless base station.
In an embodiment, the method further includes the steps of: transmitting additional information by cordless base stations wherein the information is received by cordless mobile parts and indicates that the emergency calls can be passed onto the emergency call service points via the cordless base stations; and synchronizing first cordless mobile parts, which receive the additional information from first cordless base stations, and to which the first cordless mobile parts do not have any access authorization, as a precaution for making emergency calls, at least temporarily with the first cordless base stations for a telecommunication which is restricted to making emergency calls.
In an embodiment, the cordless telecommunications system is a DECT/GAP system.
In an embodiment, the cordless telecommunications system is a PHS system.
In an embodiment, the cordless telecommunications system is a WACS system.
In an embodiment, the cordless telecommunications system is a PACS system.
In an embodiment, the cordless telecommunications system is a CDMA system.
In an embodiment, the cordless telecommunications system is a TDMA system.
In an embodiment, the cordless telecommunications system is an FDMA system.
In an embodiment, the cordless telecommunications system is a hybrid system of a CDMA system, a TDMA system and an FDMA system.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.